This application relates to an endogging log transport apparatus and, more particularly, to an endogging apparatus with dual carriages for transporting logs from a log charger and through log breakdown elements.
Endogging carriages are used in lumber mills to transport unprocessed logs from a log charger through the breakdown elements such as chippers, bandsaws, circle saws and the like. The carriage has dogs mounted thereon which grasp the log, remove it from the log charger and transport it lengthwise through the log breakdown elements where the log is processed. The carriage then returns unloaded from the breakdown elements to the log charger where it retrieves another log and repeats the process.
The process is inefficient. While the log charger has the capability of supplying a steady stream of logs to the carriages with little delay therebetween, there is a lengthy time delay between successive log grasping steps while the carriage moves the first log from the charger through the log breakdown elements and returns. While the speed of the process may be increased by providing well functioning machinery, it is inherently limited by the process. While it has been possible to provide a second carriage, such a carriage could only be used with an additional charger and additional breakdown equipment which, again, is inefficient for precisely the same reasons as explained.
Yet another disadvantage in present log transport apparatus is the arrangement used to prevent the carriages transporting logs from leaving the rails on which they move. The loads applied to the carriages when grasping, transporting and releasing logs are unpredictable, include impacting and acting in a variety of directions on the carriages which tend under some conditions to remove the carriage, usually upwardly, from the rails. To obviate this possibility, a "hold down" wheel has been used in some prior apparatus which acts vertically downwardly on the carriages and thus prevents the carriages from moving upwardly off the rails. This requires additional equipment and increases costs.
U.S. Pat. No. 3,756,296 issued to Bo Ackerfeldt, discloses a log processing apparatus having a pair of carriages running on laterally spaced apart main rails which are disposed on opposite sides of a feed axis of log processing or breakdown equipment. Each carriage has a pair of downwardly extending log holding arms or dogs which are off-set inwardly from the carriage towards the feed axis so that gripping means of the dogs are on the feed axis. The dogs of one carriage are extended to a lowered position for gripping a log for feeding the logs forwardly through the apparatus, while concurrently the second carriage, with retracted dogs, moves in a reverse direction, passing the first carriage without interference therewith due to retracted dogs. The first carriage releases the log and the second carriage engages a second log and feeds it forwardly, while the first carriage is returning with retracted dogs to pick up a third log. While this apparatus discloses a pair of carriages which reciprocate in opposite directions to improve throughout of logs through the apparatus, each dog grips the log with top and bottom clamps which has disadvantages as follows.
The top clamp of each dog requires a vertical movement which is separate and distinct from the horizontal movements necessary to adjust the spacing between the dogs to accommodate logs of different lengths. This introduces additional adjustments, which necessarily slows down the grasping of the log prior to transportation to the log breakdown apparatus. Guide rails spaced vertically below the main rail guide the carriage and lower ends of the dogs. The provision of a lower dog guide rail and bottom jaws of the clamping apparatus of this patent obstructs the lower surface of the log. This obstruction prevents machining of the lower surface of the log while it is gripped by the top and bottom clamps which limits versatility and requires additional machinery stations downstream from the apparatus.